It is well known that the application of foam is useful in many industries from shaving cream, to food products to fire suppression. The quality of the foam, the liquid to gas ratio of the foam, the ability to use non-combustible gases, the ability to use non-corrosive and inert foaming agent, the ability to produce a biodegradable inert and safe for human contact foam and the distance that the foam can be sprayed and ultimate use are factors relevant to the design and operation of foaming apparatus.
Carroll et al., U.S. Pat. No. 5,058,809, is representative of a foam generating nozzle designed to aspirate ambient air into a flowing aqueous stream containing a foam producing agent. Foam is produced and discharged from the outlet of the nozzle. It is also known to incorporate a deflection or impingement structure in a foam-generating nozzle to facilitate mixing and increase foam production, as shown in Nysted, U.S. Pat. No. 4,330,086.
In the fire suppression industry, there are a number of drawbacks associated with foam generating nozzles. Since air contains oxygen, foam generated from using air as the gas is not ideal for smothering a fire. Also, many of the nozzles operate as ejectors, that is, the kinetic energy of the flowing aqueous stream is used to draw air into the nozzle. The principle of conservation of momentum results in a decrease in the velocity of the aqueous stream. Furthermore, deflection and impingement structures provided in the nozzle can increase the resistance to fluid flow through the nozzle.
Urquhart et al., U.S. Pat. No. 2,106,043, discloses a method for generating foam in which a non-combustible gas is mixed with an aqueous foam forming mixture in a foam forming chamber. The entering gas is distributed in the foam forming chamber under pressure, wherein the pressure of the gas is sufficient to carry the foam from the chamber through the hose and nozzle attached thereto. The gas is introduced perpendicular to the flow of the aqueous mixture.
Foam-generating devices having a mixing manifold in which the gas is injected at an angle of less than 90 degrees relative to the flow direction of the foam forming liquid solution, are disclosed in Mahrt, U.S. Pat. No. 5,881,817, and Henry, U.S. Pat. No. 6,112,819. Neither of the aforementioned references, however, contains jets or other means to increase the velocity of the foam-forming liquid, prior to the foam-forming liquid making contact with the gas being injected into the mixing manifold.
However, none of these attempts at a method and apparatus for generating foam are efficient, cost effective to manufacture or use atomizing and turbulence for the manufacturer of foam in a mixing chamber.
Therefore, it is an object of this invention to manufacturer an efficient, pressure operated, foam generating method and apparatus.